Automotive racing continues to be refined as the equipment and driving techniques advance toward optimum performance. In one class of racing, professional circle track racing, often, the automobile's engine performance is measured in the laboratory on a dynamo meter which measures the engines torque, speed and power characteristics. Particular engine characteristics, together with transmission design, rear-end ratios, tire parameters, suspension set-up, and other vehicle characteristics, together result in actual "on track" vehicle racing performance. While the optimum rpm for a given vehicle may be established in the laboratory, this optimum rpm value will obviously vary from one vehicle to the next.
In professional circle track racing, the peak vehicle performance for a given set of track conditions tends to fall within a narrow band of engine rpms, given the other vehicle components such as transmission, tires, suspension, etc. as noted above. This peak performance or optimum range of engine rpm can be established in the laboratory as also noted above. For example, a variation in engine rpm of only as much as 50 rpm while entering or exiting a corner could require a small gear change in the differential. Accordingly, it is important that a racing tachometer give an accurate reading of engine rpm in a form in which the driver can best ascertain and utilize the information.
During a race, the engine rpm is measured by vehicle instruments and displayed to the driver by the tachometer. A digital tachometer can be very precise and display engine rpm down to several places. However, with rapid, slight variations in engine rpm, it is difficult for the average driver to quickly read and interpret the rapidly changing display of the digital tachometer. Accordingly, an analog display of rpm information, that is an analog tachometer display, is generally preferred in racing.
In most analog tachometers, a pointer rotation of approximately 250 to 270 degrees is provided. The diameter of the tachometer face may vary; however, even with a relatively large diameter face of the tachometer, with the requirement that the reading go from 0 to approximately 10,000 rpm, usually the minimum usable scale division which can be marked on the face of the dial is approximately 100 rpm. Such a scale division would result in division markings approximately 120 inches apart on a 5 inch diameter tachometer dial face. However, in practice, for purposes of maintaining peak vehicle performance as mentioned above, often as little as 20 rpm variation in engine speed can be significant. Thus, with minimum usable divisions representing 100 rpm, a variation of 20 rpm is difficult or impossible to read or identify. Thus, it is difficult with present tachometers for the racing driver to determine small yet significant variations from the optimal or peak performance rpm.
As a related matter, the peak or maximum rpm on a vehicle generally occurs immediately prior to gear shifting. Drivers often train heavily on effective gear shifting. Not only should the driver shift quickly and cleanly, but the driver should also shift at the appropriate engine speeds to extract the maximum power and racing speed from the vehicle. In oval track racing it is unlikely that the driver would over-rev the engine in high gear, but it is possible that he may have over-reved while accelerating through the gears. This could cause damage to the valve train which will be important information for the crew chief. While various rpm memory devices have been provided in the past for recording and recalling peak engine rpm, one aspect of the present invention provides an improvement in a peak or valley rpm memory.
A present invention improves on the above-noted situation regarding tachometer readings in that it allows for two different operational modes. In a first mode, the tachometer functions as a traditional instrument providing analog engine rpm information in a relatively wide range, such as from 0 to 10,000 rpm as the vehicle accelerates to competitive racing speed. In a second or "Power Band" mode, after the vehicle reaches competitive racing speed, the dial operation is in effect expanded. For example, the first or "normal" tachometer mode might have major dial divisions in 1,000 rpm increments with minor dial divisions in 100 rpm increments. However, the "Power Band" mode might have a full meter range of only 1,000 rpm, such that each major division represents 100 rpm and each minor division is equivalent to 10 rpm. Thus, the driver can more accurately determine relatively small changes in rpm of the engine with the Power Band mode in effect, and therefore more accurately maintain near peak performance.
Moreover, the present invention makes possible the selection of a nominal peak performance rpm as a center value of the Power Band range. Thus, any peak performance rpm which has been established in a laboratory or elsewhere can be selected as the "Power Band" center value on the meter in the present invention. The Power Band range will then read positive or negative increments to either side of this peak performance center value.